Friday, August 31, 2012

Before understanding the concept of Logical Volume Manager(lvm Linux), need to understand the actual or current volume management and its drawbacks. There are many drawbacks in current volume management as follows:

·Suppose, we have one partition, which is mounted in Linux system. Its size 50GB. And after totally occupied the space in this partition, we need to change mount point. i.e. if there is free space in same hard disk then we can create a new partition and the mount it to new directory and send new data to there or we need to add new hard disk. But we can't increase the volume of first partition, always need to create new partition and mount it to new directory and it is not feasible solution.

·For backup purposes, we are not able to take snapshots of data. So it is not very good for backup purposes also.

Logical volume manager overcome these drawbacks. In this, we can extend the partition size when we need to increase it or decrease it. Along with this, it is useful while backup because we can take snapshot of data at certain time. And that much of data, we can backup.

Take care – Volume and Partition are interchangeably words but these are different things. Volume Management is a approach to dealing with disks and partitions. Instead of viewing a disk or storage entity along partition boundaries, the boundaries are no longer there and everything seems a volume.

There are three concepts are most important in Logical volume management. They are as follows:

·Volume Group(VG): Volume group is the group of physical volumes. If there are 3-4 physical volumes or hard disks then they are united in Volume group and seems a single volume. It can extend or reduce.

·Logical Volume(LV): Logical volume is the part of volume of VG. We can extend the size of LV as well as reduce it. For extension of LV need free space in VG. And suppose we reduced the LV then free space added in VG's free space.

lvm raid is different concept in linux lvm. actaully, lvm we can use in raid as well.